This disclosure relates generally to a clamp assembly for use with a positioning system used to position body parts, such as a knee, during a medical or surgical procedure. The term knee, as used herein, is intended to be synonymous with a knee joint. More particularly, the system is used to first position the bones of the knee in a desired position and orientation. The position of the knee can be adjustably set along a plurality of different axes. Once the position of the knee is set, the system holds the knee in that position and orientation to facilitate the performance of a procedure on the patient. Although the particular embodiments described herein are described in relation to positioning a patient's knee, it should be understood that one of ordinary skill in the art could modify the concepts herein for positioning other parts of the body.
When a medical or surgical procedure is performed on a limb, such as an arm or leg, it may be desirable to restrict movement of the limb. Without holding the limb steady, it can become extremely difficult for the practitioner to perform procedures on the limb with precision. Further, with an increasing frequency, surgical procedures are performed with the aid of surgical navigation systems. This type of system often includes one or more trackers and a camera, for example.
In one version of such a system, at least one tracker is attached to the patient. Based on the signals emitted by the tracker, the camera and associated software determines the position of the tracker. By extension, this leads to the determination of the position of the attached patient. (Some surgical navigation systems have trackers with units that, instead of emitting energy, track energy emitted from the static source.) For many surgical navigation systems to operate, the trackers and camera must be in close proximity to each other. This means that it may be necessary to restrain the movement of the limb so that the tracker and complementary camera are able to engage in the appropriate signal exchange. Such surgical navigation systems are described more fully in U.S. Pat. No. 7,725,162, titled “Surgery system,” the entire contents of which are hereby incorporated by reference herein.
Presently there are a number of different devices that can be used to hold the limb of the patient. These devices include some sort of shell or frame designed to receive the limb. Structural members hold the shell or frame to the operating table. At the start of the procedure, the patient's limb is placed in the shell. The shell is positioned at a location which preferably provides the practitioner with sufficient access to perform the procedure. If a navigation unit is used to facilitate the procedure, the shell is further positioned to ensure that any components of the system fitted to the patient are within the appropriate range to the complementary static components of the system. One particular limb positioning system is described in U.S. Patent Publication No. 2013/0019883, the disclosure of which is hereby incorporated by reference herein.
Some available limb holders are able to hold the limb of the patient in a fixed position, while other limb holders allow for movement of a portion of the limb. In either instance, a portion of the limb holder is typically attached to the operating table. A rail is commonly mounted on the table to promote this attachment.
It is common practice to place a sterile drape on the operating table prior to placing the patient on the table. This drape functions as a sterile barrier. If a portion of the limb holder is attached to the table, then it can be difficult, if not impossible to, place the drape around and/or under the attached portion of limb holder so as to provide the desired sterile barrier. Therefore, the drape is often place between the table and the attached portion of the limb holder. For example, the drape may be placed between the interior surface of a clamp assembly and a rail that is mounted on the table and engageable with the clamp assembly. Preserving this sterile barrier is important for patient safety, however, many known limb holders have a clamp assembly that may be likely to rip or tear the sterile drape, causing a loss of the desired sterile barrier.